The present invention relates to thermostatic assemblies incorporating a heat-expandable bellows having an integral work member, such as a valve plug which is moved with the expansion of the bellows to alter an opposed elements, such as to close an opposed valve opening.
Due to the eccentricities and tolerances of a bellows assembly and/or an associated housing, such as a valve body incorporating a valve opening, bellows assemblies must be precision-manufactured so that the valve plug or other work member is aligned to be concentric with the valve opening or other opposed element. Otherwise, the plug will not seat properly in the valve opening when the bellows expands, causing wear, leakage or undesired stresses.
In order to improve the ability of a bellows assembly to properly seat in a valve opening, thereby avoiding wear, leakage and undesired stresses, it is known to provide a swivel attachment between the bellows assembly and the valve housing. Reference is made to U.S. Pat. Nos. 1,076,159; 1,738,248; 1,929,684 and 4,560,105 for their disclosures of different swivel attachment structures for bellows assemblies.
The main disadvantages of known swivel bellows assemblies relate to the cost of producing and assembling the precision-mated parts thereof, and the requirement that the valve housing must be customized to incorporate a swivel base or socket for the swivel bellows.